As the title suggests I'm torn between the two for a balanced video card that can give me good frames on games like Arma 2 OA and Shogun 2, but also decent render times and computing power. I've done my research and have come to the conclusion that the 580 is great for CUDA and open GL as well as decent for games, but the 670 is a monster for games with quantity over quality. I want to be using things like fumefx, 3ds max, vray, zbrush. I know for a fact that 3ds max uses CUDA technology and I really need that boost for my rendering which the 580 is adept in, but at the same time I hear the 670 has 30% more performance in games. My question is will the 670 with its crippled computing power still give me decent render times in SLI?